Induction of transforming growth factor beta 1 by insulin-like growth factor-1 in dermal fibroblasts.
Transforming growth factor beta1 (TGF-beta1) belongs to a family of multifunctional modulatory proteins involved in cell growth, differentiation, development, and wound healing. Although the biological activities of TGF-beta1 have been extensively studied, its regulation remains obscure. Here we report the effects of insulin-like growth factor-1 (IGF-1) on the expression of TGF-beta1 by dermal fibroblasts and suggest a possible mechanism. An enzyme-linked immunosorbent assay (ELISA) specific for TGF-beta revealed a greater than twofold increase (12.3 +/- 1.6 vs. 4.8 +/- 0.8 pg/10(4) cells, n = 7, P < 0.05) in the protein in conditioned medium obtained from IGF-1-treated cells compared to that from untreated controls. Similar results were obtained by the mink lung epithelial cell growth inhibition assay. The results of Northern analysis revealed a dose-dependent increase in TGF-beta1 mRNA in response to IGF-1 treatment. Using the optimum concentration of IGF-1 (100 ng/ml), a greater than twofold increase (25.43 +/- 5.7 vs. 12.13 +/- 4.5, P < 0.05) in TGF-beta1 mRNA was observed. This effect persisted for at least 48 h after IGF-1 was removed from the culture medium. Nuclear run-on assay showed that this stimulation was due, at least in part, to an increase in the rate of transcription of the TGF-beta1 gene. Treatment of human dermal fibroblasts with IGF-1 caused a substantial increase in c-fos and c-jun mRNA expression within 30 and 60 min, respectively. In contrast to c-jun mRNA which was constitutively expressed by dermal fibroblasts, the expression of c-fos mRNA was transient and only detectable between 15 and 60 min. Greater than 58% of the increase in TGF-beta1 caused by IGF-1 could be blocked by the addition of anti-TGF-beta1 neutralizing antibody to the culture medium, suggesting that autoinduction of TGF-beta1 may be involved. An increase in IGF-1-induced TGF-beta1 should be important in many different physiological processes such as cellular proliferation, differentiation, and wound healing. These findings also suggest that induction of TGF-beta1 mRNA and protein by IGF-1 may be a mechanism by which this cytokine is regulated in physiological and/or pathological conditions.
Ghahary
A
A
Department of Surgery, University of Alberta, Edmonton, Canada.
Shen
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Q
Shen
Y J
YJ
Scott
P G
PG
Tredget
E E
EE
D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D016762:Genes, fos / Q000187:drug effects; D016758:Genes, jun / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D008168:Lung / Q000166:cytology; D008907:Mink; D012333:RNA, Messenger / Q000096:biosynthesis; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000187:drug effects
D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I